This is a fossil tooth from extinct toothed whale (ODONTOCETE), of a Pygmy Dwarf Sperm whale. It was found in a fossil shell pit in Florida hence the white hue. It dates to the same period as the giant Megalodon shark - the Miocene / Pliocene Period. The white color is from the nature of the shell pit deposit, unlike underwater specimens that are dark and with denser mineralization. Complete fossil whale teeth from a shell pit, are very, very rare and it takes countless hours of fossil hunting in the shell pits to be fortunate enough to find just one that is complete and with its unbroken, sharp tip like this!
Whale fossils are perfect to display alongside a shark tooth collection as whales would have shared the same waters and time period as many of the dangerous sharks found off the East Coast of North America during the Miocene / Pliocene Period, including the infamous MEGALODON shark. Megalodon sharks would have been the primary predators of these whales and often, fossils from whales, are found with fossil Megalodon teeth, indicating a Megalodon "kill / feeding site".